JPH0494228A - Dynamic channel allocation method - Google Patents

Abstract

PURPOSE:To avoid collision between time slots used by other base station by detecting a period of a carrier used by the other base station, comparing the period with the period of a carrier used by its own base station and detecting the approach of the time slot of its own base station with the time slot of the carrier used by the other base station based thereon. CONSTITUTION:Each of base stations KS1, KS2 and each of mobile stations PS1, PS2 use a different time slot of a same frequency as that of a channel used for receiving a communication signal toward its own station, receive a communication signal of other station making communication with independent synchronization to its own station so as to measure an interval between a time slot used by the other station and a time slot used by its own station. Then before collision between the time slot used by its own station and the time slot used by the other section takes place, an idle channel not used by all stations is detected and the channels used by its own station and an opposite station being a communication opposite party to its own station are simultaneously transited to the detected idle channel. Thus, the collision with the time slot used by the other base station is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to multi-carrier time division multiple access (Ti
me Division Multiple Access
This relates to a frequency allocation method for a digital mobile phone system that communicates using the SS (hereinafter referred to as TDMA) method, and prevents interference between multiple digital mobile phone systems that are asynchronous to each other. This invention relates to a frequency allocation method that avoids interference caused by.

BACKGROUND OF THE INVENTION In recent years, mobile communications have become extremely popular, and in particular, the spread of mobile cellular phones has been remarkable.

Now, in the current mobile phone, frequency division multiple access (Frequency Division Multiple Access) is used to perform one-to-one wireless communication using a specific frequency between a mobile station and a base station connected by wire to a fixed telephone network.
A Multiple Access (hereinafter referred to as FDMA) method is adopted.

In this FDMA mobile phone system, the selection range of usable carriers for each system is set to be different from each other, and as a result, each system is allowed to exclusively use different carriers. . Therefore, there is no need to consider the possibility that the systems share the same carrier.

On the other hand, in contrast to multiplex communication using the FDMA method described above and multiplex communication using a different method, the TDMA method performs multiplex communication by time-sharing carriers of one frequency. In particular, each of a plurality of carriers is divided into a plurality of time slots, and communication between a fixed central station and a terminal station is carried out on a channel consisting of a pair of the above carrier and time slot. Multicarrier TDMA signal communication is often used, which is performed using a selected vacant channel that is not used for communication between another central station and a terminal station.

In conventional multicarrier TDMA multiplex communication between fixed central stations and terminal stations, the selection range of carriers that can be used for each fixed station communication system is set to be different from each other. Because each system uses a dependent synchronization method in which fixed terminal stations synchronize in a subordinate manner to a fixed central station, interference between terminal stations within the same fixed station communication system does not occur. In addition, by setting different carrier selection ranges between each system, it is not necessary to consider the possibility that each system may share the same carrier, similar to the FDMA communication described above. ing.

By the way, in the digital mobile phone systems and car phone systems mentioned above, one base station within each system can access multiple mobile stations, reducing the number of installed base stations and reducing costs related to base stations. Alternatively, adoption of a multi-carrier TDMA system is being considered in order to be able to cope with an increase in the number of subscribers without increasing the number of installed base stations.

In the TDMA system in the above-mentioned digital mobile cell phone system or car phone system, a base station corresponds to a central station in conventional TDMA communication between fixed stations, and a mobile station corresponds to a terminal station.

However, in the digital mobile phone system and car phone system, each terminal station is a mobile station and not a fixed station, so the carrier frequency used by each base station and each mobile station is fixed. It is difficult to

For this reason, the carrier used by each base station and each mobile station pair is not fixed, and when the pair of each base station and each mobile station, which is normally in standby mode on a fixed carrier, starts communication. The premise is that this is done through dynamic channel allocation, which searches for an empty channel among multiple carriers and transfers to this empty channel for communication.

In this case, for the latter car phone system, TD
Since the car phone base station, which is the central station of MA, is connected to the car phone network, the base stations of each car phone system are subordinately synchronized to the car phone network, so that the communication between each base station is Synchronization, i.e.
Can maintain synchronization between each car phone system,
Each base station can stably allocate time-divided time slots to each terminal station so that interference between car telephone systems does not occur.

Problems to be Solved by the Invention On the other hand, with respect to the former mobile cell phone system, unlike the case of the above-mentioned car phone system, the network to which this system is connected is , PSTN) and private branch exchanges (hereinafter referred to as PBX), it cannot be expected to obtain synchronization from the network side for slave synchronization with these networks. Each base station of the mobile phone system independently generates a transmission lock.

By the way, in the conventional mobile cell phone system described above, each system selects a carrier to use from among carriers in different ranges, so the carrier selected by each base station is uniform throughout the entire system. There is no need to manage this, and therefore no equipment is provided for this purpose.

For this reason, TDMA is added to the above conventional mobile phone system.
If this method is adopted, base stations in other systems cannot mutually confirm whether they have selected carriers, which creates the possibility that base stations in multiple systems select the same carrier. Ru.

However, in this case, as mentioned earlier, the base stations in each system generate transmission locks independently, so if the transmission lock frequencies of the base stations in each system are not synchronized and the same carrier If there is a difference in the width of the mutual transmission lock between the plurality of base stations selected, the synchronization timing of the time slot for each system will be different.

This state is shown in FIGS. 5 and 6.

First, FIG. 5 shows a state in which base stations KSI and KS2 of two different systems start communication with mobile stations PS1 and PS2, respectively, using different time slots of the same carrier. This is a timing chart shown in pulses, and in FIG. 5, the upper row shows the communication state at one base station KSI, and the lower row shows the communication state at the other base station KS2.

In FIG. 5, one scale on the horizontal axis indicates one time slot, and the numbers located above and below the horizontal axis indicate the number of the time slot. Also, the time slots located above the horizontal axis are from the base station KSI, KS2 side to the mobile station PS side.
I, means the time slot for transmitting to the PS2 side, and the time slot located below the horizontal axis means the time slot for transmitting to the mobile station psi, PS2 side empty base station KSI, KS2 side. are doing.

Furthermore, the boxed time slots are the base station KSI
and mobile station PS1, and base station KS2 and mobile station PS2.
The pairs and indicate the time slots that have been individually acquired and used for communication.

In FIG. 5, one base station KSI starts communication in a first time slot on a certain carrier, and the other base station KS2 starts communication in a third time slot on the same carrier. .

However, since these two base stations KSI and KS2 are asynchronous and their transmission locks are generated individually, the time slot intervals set individually at each base station KSI and KS2 are not necessarily the same. It doesn't match.

If the transmission lock intervals generated individually in each base station KSI and KS2 do not match, a difference will occur in the slot length of each time slot, and for example, if one base station KSI and mobile station PS1 If the time slot length of the pair of base station KS2 and mobile station PS2 is shorter than the time slot length of the pair of base station KS2 and mobile station PS2, as time passes, base station KS
The third time slot used in 2 will be shifted backwards.

Therefore, at the start of communication, the interval between the first time slot used by base station KSI and the third time slot used by base station KS2 is 2.5 to 3.5 slots. However, after a certain amount of time passes from the state shown in Fig. 5 above, as shown in Fig. 6,
The interval before and after the mutual time slots gradually decreases, and the time slots become close to each other, which may cause interference between the two transmission signals.

In other words, the time slots that each base station KSI and KS2 acquire and start using after confirming that there is no mutual interference at the start of communication gradually become as shown in FIG. 6 due to the time relationship shown in FIG. are close to each other, and eventually a collision with the time slots used by other base stations occurs.
There was a problem in that the call quality deteriorated.

The present invention solves the above-mentioned conventional problems. Before a collision occurs between the time slot used by the own base station and the time slot used by another base station, it is possible to It is possible to change the channel used by the own base station by reselecting the channel and avoid collision with the time slot used by other base stations. It is an object of the present invention to provide a frequency dynamic allocation method that allows a multi-channel TDMA system to be introduced into a cordless telephone system.

Means for Solving the Problems In order to achieve the above object, the present invention provides a network-connected
Communication via mobile radio links between multiple base stations that generate synchronization independently of each other and mobile stations served by those base stations is performed using multiple frequencies and multiple times at each frequency for each base station. Multi-channel time division multiplexing/time division duplex communication using a communication signal transmission channel consisting of a set of frequency and time slot, in which the frequency and time slot to be used can be selected from among the slots. Each base station and each mobile station uses a different time slot with the same frequency as the channel used to receive communication signals directed to its own station, and synchronizes independently with respect to its own station. Receive communication signals from other stations that are communicating, and check the time slots that other stations are using.
Measure the interval between the time slots used by the own station, and based on the measurement results, predict collisions between the time slots used by the own station and the time slots used by other stations. Then, based on this prediction result, before a collision occurs between the time slot used by the own station and the time slot used by the other station, all stations will be able to find unused channels. is detected, and the channels used by the own station and the opposite station with which the own station communicates are simultaneously changed to the detected empty channel.

Furthermore, in order to achieve the above object, the present invention allows each base station and each mobile station to use a different time slot having the same frequency as the channel used for receiving communication signals directed to the own station. It receives the communication signals of other stations that are communicating independently and synchronously with respect to the station, and the communication signals directed to the own station, detects the received signal level of each of these communication signals, and detects the received signal level of each of these communication signals. When a collision between the time slot currently being used and the time slot used by the other station is predicted, the reception level of the communication signal of the other station is compared with the reception level of the communication signal for the own station. Through this comparison, when it is recognized that the reception level of the communication signal of the other station is sufficient to interfere with the communication signal directed to the own station, the time slot used by the own station is determined. Before a collision with the time slot used by the other station mentioned above occurs, all the stations detect an unused free channel and use the detected free channel between the above own station and the own station. The channel used by the opposite station of the communication partner can be changed at the same time.

Therefore, according to the present invention, the period of the carrier used by another base station is detected and compared with the period of the carrier used by the own base station, and based on this, the period of the carrier used by the other base station is detected. Each base station establishes frame synchronization by generating mutually different transmission locks by detecting the proximity to the time slot of the carrier being used by each base station. Before a collision with the time slot used by another base station occurs, you can reselect another free channel and change the channel to be used, thus avoiding collision with the time slot used by other base stations. Therefore, a multi-channel TDMA method can be easily introduced into a cordless telephone system using a plurality of existing FDMA methods that are asynchronous to each other.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. In this embodiment, signal transmission over a mobile radio line between a base station connected by wire to a network such as PSTN or PBX such as 15DN, and a mobile station connected to this base station via a mobile radio line. TDM on one carrier
A method (hereinafter referred to as TDMA/TD) that simultaneously realizes A method communication and time division duplex (hereinafter referred to as TDD) method communication.
8-channel multicarrier TDM
An example of a digital mobile phone system that performs multiplex communication using the A/TDD method will be explained.

1. Signal transmission over a mobile radio link (Figures 1 and 2) As mentioned earlier, signal transmission between a base station and a mobile station via a mobile radio link is carried out over a single carrier. T
This is performed using 8-channel multiplex communication using the DMA/TDD method.

In order to realize the 8-channel multiplex communication using the TDMA/TDD method, a TDMA frame, which will be described below, is used as a frame format during signal transmission.

1-1. TDMA frame (Figure 1) This TDMA
A frame is used in the transmission format of the 8-channel TDMA/TDD system,
The ITDMA TDMA frame is determined based on the transmission lock generated at each base station, and if the period is T seconds, the ITDMA TDMA frame is divided into 16 time slots.

This is an ITD in order to realize TDD signal transmission.
This is because the second half of the MATDMA frame is divided into two blocks, and the first half and second half are each divided into eight time slots in order to realize TDMA signal transmission with eight channels multiplexed. The contents are shown in Figure 1.

As can be seen from Figure 1, the above TDMA frame is T
In order to realize DD method signal transmission, the first half is allocated to base station transmission/mobile station reception (downlink), and the second half is allocated to mobile station transmission/base station reception (uplink), and 8-channel TDMA is used.
In order to realize signal transmission using this method, each of the first half and second half is further divided into a total of eight time slots (hereinafter referred to as TS) from the first time slot to the eighth time slot (hereinafter referred to as TSI to TS8). It is divided.

Each base station and mobile station is normally in a standby state on a fixed carrier assigned for transmitting control signals common to the system, and at the start of communication, downlink is used to transmit signals between each other. TSI to T for line and uplink
An empty channel that is not used for communication between another base station and a mobile station is selected from a set (channel) of S8 and a plurality of carriers allocated for communication.

Thereafter, the base station and mobile station use the selected free channel to transmit communication signals between them in a burst manner.

1-2. Structure of a channel burst signal (Figure 2) When an empty channel for communication between a base station and a mobile station is selected and acquired, signal transmission between them is performed in bursts on this empty channel. However, in that case, the channel burst signal output from the base station and mobile station using one TS has a structure as shown in FIG.
Guard space (hereinafter referred to as
(referred to as GS) and a lamp part (hereinafter referred to as R
) is set.

After the above R, a preamble signal (hereinafter referred to as PA) for establishing focus synchronization on the receiving side of this channel burst signal is assigned, and this P
After A, a frame synchronization signal (hereinafter referred to as FS), which is a signal for transmitting a unique word, is assigned to provide a synchronization point for the burst signal to the receiving side.

Furthermore, following the above FS, a low-speed auxiliary control channel (hereinafter referred to as 5ACCH) is allocated for transmitting control signals during communication, and following this 5ACCH, user signals such as voice signals are transmitted. A traffic channel (hereinafter referred to as TCH) is allocated for the purpose of the communication, and finally R is allocated again.

2-2. Configuration of base station and mobile station (Figures 3 and 4) A base station is used for wireless transmission and reception with mobile stations, and as mentioned earlier, it performs TDMA communication with mobile stations. /
It performs 8-channel multiplex communication using the TDD method. That is, it can be accessed by up to eight mobile stations simultaneously.

Each base station individually generates and supplies a clock for the mobile station to achieve slave synchronization with the base station, which will be described later.

On the other hand, a mobile station accesses the nearest base station to communicate with the network, and this access is achieved by mutual transmission and reception of control signals with the base station on a fixed carrier.

2-2-(1) Configuration of base station (FIG. 3) The schematic configuration of the base station as described above will be explained based on FIG. 3. still,
In the following description, "down direction" indicates signal transmission from the base station side to the mobile station side, and "up direction" indicates the opposite.

In FIG. 3, 301 is a PSTN or PB (not shown).
This is a network control unit connected to networks such as Ru.

302 is connected to the network control unit 301, and in the downstream direction, a codec analog/digital conversion unit (hereinafter referred to as codec A/D conversion unit) receives communication signals from the network side separated by the network control unit 301. ), and
It converts communication signals such as encoded voice signals from the network side into analog.

303 is connected to the codec A/D converter 302;
In the downstream direction, it is a buffer memory section to which analog-converted communication signals are input in bursts, and temporarily stores the input communication signals.

304 is a clock oscillation circuit that generates a timing pulse that is a reference for transmission lock between this base station and a mobile station that accesses and communicates with this base station, and this timing pulse is transmitted to each base station. It is generated independently and individually for each.

305 is a network control unit 301 and a buffer memory unit 303;
In the downstream direction, the network control unit 301
This is a communication control unit to which a control signal from the network side separated by the buffer memory unit 303 and a communication signal stored in the buffer memory unit 303 are input, and searches for an empty channel when a control signal from the network side is input. , and generates and outputs to the mobile station an incoming call message for negotiating the settings of the channel to be used during communication, including information on the vacant channels detected through this search.

306 is a clock oscillation circuit 30 in the downstream direction.
4, a communication signal from the Hanfame Meri unit 303, and a control signal from the communication control unit 305 are input, and in the upstream direction, the transmission from the mobile station is received by the reception unit 320, which will be described later. This is a TDMA/TDD processing unit to which signals are input.

In the downlink direction, this TDMA/TDD processing section 306 generates a TDMA frame for transmitting a signal to a mobile station based on a communication signal and a control signal input from a buffer memory section 303 and a communication control section 305. The content of the channel burst signal as shown in FIG. 2 is determined.

Then, the transmission signal for the mobile station composed of the determined TDMA frame is outputted in bursts to the transmission unit 310 (described later) based on the timing of the timing pulse from the clock oscillation circuit 304, and at the same time, the transmission signal is transmitted. Uniso) 310 outputs a transmission activation signal instructing the activation of transmission operation.

Furthermore 1. j7) In the uplink direction, the TDMA/TDD processing unit 306 c, among the transmission signals from the mobile station inputted from the receiving unit 32 o (described later), controls the control signal to the communication control unit 305 and the communication signal to the buffer memory unit 303. The FS included in the transmitted and received transmission signals, that is, the channel burst signals, is transmitted to this TDMA/TDD.
This is monitored by a frame synchronization detection circuit (not shown) provided in the processing unit 306.

In addition, in the upstream signal transmission, the TDMA/T
The buffer memory unit 303 to which the communication signal from the DD processing unit 306 is input temporarily stores this communication signal and sends it to the network control unit 301 in bursts.

On the other hand, the communication control unit 305 to which the control signal from the mobile station is input via the TDMA/TDD processing unit 306 controls communication signal transmission between the own base station and the mobile station based on this control signal. , and notifies the TDMA/TDD processing unit 306 of the determined channel.

Then, the TDMA/TDD that received the notification of this channel
The processing unit 306 notifies a transmitting unit 310 and a receiving unit 320, which will be described later, of the carrier frequency of the determined channel.

Incidentally, the TDMA/TDD processing section 306 is connected to a transmitting unit 310 and a receiving unit 320 for performing line transmission and reception with a mobile station. Therefore, the configurations of the transmitting unit 310 and the receiving unit 320 will be explained below.

First, in the transmitting unit 310, 311 is a TDM
Connected to the A/TDD processing unit 306, TDMA/TD
a modulation unit that modulates the transmission signal from the D processing unit 306;
A transmitter 12 is connected to the modulator 311 and transmits a modulated transmission signal to a mobile station via an antenna 330 and a mobile radio line (not shown).

On the other hand, in the receiving unit 320, 321 is a receiving section to which a transmission signal from a mobile station is input via a mobile radio line and an antenna 330, and detects the reception level of the received transmission signal from the mobile station. The TDMA/TDD processing unit 306 is notified of this as an electric field detection signal.

Further, 322 is connected to this receiving unit 321 and is a digital signal (digital) which demodulated the received transmission signal from the mobile station.
This is a demodulation unit that outputs the signal to the TDMA/TDD processing unit 306.

Further, the transmitter 312 and the receiver 321 and 1. The antenna 330 is connected to the TDMA/TDD processing section 306, and transmits its connection direction based on the timing pulse input from the synchronization control section 302<based on the instruction from the TDMA/TDD processing section 306. An antenna switch 340 that switches between the section 312 side and the receiving section 321 side is interposed.

This antenna switch 340 is for switching the transmission and reception status of the base station in accordance with the timing of the downlink communication and uplink communication areas of the TDMA frame in the transmission formant on the mobile radio line, and is always on. The connection direction is switched to the receiving unit 321 side so that control signals are received on a fixed carrier.

This antenna switch 340 and the transmitter 31
2 is configured to receive a transmission activation signal output from the TDMA/TDD processing section 306, and based on this transmission activation signal, the antenna switch 340 switches its connection direction to the transmission section 312 side. The transmitter 312 outputs a transmission signal to the mobile station, which is input from the TDMA/TDD processor 306 via the modulator 311.

Further, the transmitting section 312 and the receiving section 321 include synthesizer sections 313 and 32 that oscillate variable frequencies, respectively.
3 is connected, and is used to arbitrarily change the frequencies transmitted and received by the transmitting section 312 and the receiving section 321 based on instructions from the communication control section 305.

Each of the synthesizer units 313 and 323 allows the transmitting unit 312 and the receiving unit 321 to constantly transmit and receive control signals in accordance with a fixed carrier for transmitting control signals under the control of the communication control unit 305 when this base station is in the standby state. When communicating with the network, the oscillation frequency is changed in accordance with the vacant channel through which the communication signal is transmitted.

For this reason, each synthesizer section 313 and 323 includes a communication control section 30 similar to the TDMA/TDD processing section 306 described above.
The selection result of the channel for communication signal transmission from No. 5 is inputted, and the oscillation frequency is changed in accordance with this selection result.

2-2-(2) Configuration of base station (FIG. 4) Next, the schematic configuration with the base station will be explained based on FIG. 4. In the following explanation, "downlink direction" refers to signal transmission from the base station side to the mobile station side, and "uplink direction" refers to signal transmission from the base station side to the mobile station side.
shall indicate the opposite.

In FIG. 4, 401 is a microphone provided in the transmitter, 402 is a speaker provided in the receiver, 40
3 is an operation unit in which a dial key, an end key, etc. are arranged;
Reference numeral 404 denotes a display unit on which the operating status etc. of the operating unit 403 are displayed, and these constitute a baseband system.

A codec A/405 receives the audio signal from the microphone 401 in the upstream direction, and outputs the audio signal to the speaker 402 in the downstream direction.
The D converter 406 converts codec A in the upstream direction.
This is a buffer memory unit into which a communication signal (audio signal) from the microphone 401 is input via the /D conversion unit 405 .

407 is a communication control unit into which dial signals and the like are input in accordance with the operation of the dial keys of the operation unit 403 in the uplink direction, and controls connection with the nearest base station based on the calling operation by the operation unit 403; It generates a control signal to be sent to the nearest base station for connection control.

408 is a buffer memory unit 40 in the up direction.
6 and a control signal from the communication control unit 407 are input, and in the down direction, a transmission signal from the nearest base station received by a receiving unit 420, which will be described later, is input. This is the processing section.

In the uplink direction, this TDMA/TDD processing unit 408 generates a TDMA frame for transmitting a signal to the nearest base station based on a communication signal and a control signal input from a buffer memory unit 406 and a communication control unit 407. The transmission unit 4 determines the contents of the TDMA frame, and sends a transmission signal to the nearest base station composed of this TDMA frame to the transmission unit 4, which will be described later.
At the same time, a transmission activation signal is output to the transmission unit 410 to instruct the transmission operation to start.

Furthermore, in the downlink direction, this TDMA/TDD processing unit 408 receives incoming connections from each base station, which are always received in bursts by a receiving unit 420 (described later) when the mobile station is in the standby state. The communication control unit 407 sends a control signal requesting a communication signal in the transmission signal from the nearest base station, which is received by the receiving unit 420 when a call is made between the mobile station and the network. The FS included in the transmission signal, that is, the channel burst signal, which is output to the buffer memory section 406 and received is monitored by a frame synchronization detection circuit (not shown) provided in the TDMA/TDD processing section 40B.

In addition, in the down direction, the TDMA/TDD processing section 4
Buffer memory unit 40 into which the communication signal from 08 is input
6 inputs this communication signal, that is, the encoded audio signal, to the codec A/D converter 405, where it is converted into an analog signal and output from the speaker 402.

On the other hand, in the downlink direction, the communication control unit 407 receives the control signal requesting an incoming connection from the TDMA/TDD processing unit 408, generates a control signal corresponding to the input control signal, and generates a control signal corresponding to the input control signal. TDMA/TDD
It is output to the processing unit 40B.

Furthermore, the communication control unit 407 always controls the transmission and reception frequencies of a transmission unit 410 and a reception unit 420 (described later) to a fixed carrier frequency for transmitting control signals, and communicates with the network side in this mobile station. When a call is made, a signal is sent to the transmitting unit 410 and the receiving unit 420 to instruct the transmitting/receiving frequency to be changed based on the information on the communication signal transmission channel included in the input control signal. Output.

Furthermore, this communication control unit 407 performs TDMA frame synchronization of the own mobile station based on the transmission format on the mobile radio line in synchronization with the input timing of a control signal from the nearest base station that is received by the receiving unit 420 (described later). After that, the base station operates in synchronization with the nearest base station.

By the way, the TDMA/TDD processing section 408 is connected to a transmitting unit 410 and a receiving unit 420 for performing wireless transmission and reception with a base station. Therefore, the configurations of the transmitting unit 410 and the receiving unit 420 will be explained below.

First, in the transmitting unit 410, 411 is a TDM
Connected to the A/TDD processing unit 408, TDMA/TD
a modulation unit that modulates the transmission signal from the D processing unit 408;
Reference numeral 12 denotes a transmitting unit connected to the modulating unit 411 and transmitting the modulated transmission signal to the nearest base station via the air M 430 and mobile radio line.

On the other hand, in the receiving unit 420, 421 is a receiving section into which the transmission signal from the nearest base station is input via the mobile radio line and the antenna 430, and the receiving section 421 receives the transmission signal from the nearest mobile station. This is detected and notified to the TDMA/TDD processing section 408 as an electric field detection signal.

A demodulator 422 is connected to the receiver 421 and outputs a digital signal obtained by demodulating the received transmission signal from the nearest base station to the TDMA/TDD processor 408.

Further, an antenna is provided between the transmitting section 412 and receiving section 421 and the antenna 430, and the connection direction thereof is switched between the transmitting section 412 side and the receiving section 421 side based on an instruction from the TDMA/TDD processing section 408. A switch 440 is interposed.

This antenna switch 440 is activated when a control signal for a connection request from the nearest base station is input to the mobile station,
When making a call from this mobile station to the network side, the transmission and reception status of this mobile station is adjusted to the timing of the downlink communication and uplink communication areas of the TDMA frame in the transmission format on the mobile radio line. The connection direction is normally switched from the control a1 side of the TDMA/TDD processing section 408 to the receiving section 421 side.

Then, this anti-eggplant inch 440 and the transmitting section 41
2 is configured to receive a transmission activation signal output from the TDMA/TDD processing unit 408, and based on this transmission activation signal, the antenna switch 440 switches its connection direction to the transmission unit 412 side. The transmitter 412 outputs a transmission signal to the nearest base station, which is input from the TDMA/TDD processor 408 via the modulator 411.

Further, the transmitting section 412 and the receiving section 421 include synthesizer sections 413 and 42 that oscillate variable frequencies, respectively.
3 is connected, and is used to arbitrarily change the frequencies transmitted and received by the transmitting section 412 and the receiving section 421 based on instructions from the communication control section 407.

Each of the synthesizer sections 413 and 423 allows the transmitting section 412 and the receiving section 421 to constantly transmit and receive control signals in accordance with a fixed carrier for transmitting control signals under the control of the communication control section 407 when the mobile station is in the standby state. When communicating with the network, the oscillation frequency is changed in accordance with the vacant channel through which the communication signal is transmitted.

2, each synthesizer section 413 and 423 is configured to receive a transmission/reception frequency instruction signal from the communication control section 407, and change the oscillation frequency according to the frequency instructed by this instruction signal. It looks like this.

2-2-(3) Call operation between base station and mobile station Next, the operation of each station during call origination and reception between the base station and mobile station with the above configuration will be briefly explained.

During standby, each base station and mobile station receives control signals transmitted from surrounding base stations and mobile stations using fixed carriers for transmitting control signals.

Then, the communication control unit 407 of each mobile station establishes a TDMA frame cycle for making the mobile station subordinate to the nearest base station, in accordance with the FS included in the channel burst signal from the nearest base station. Thereafter, when communicating with the network side, signals are transmitted and received at the cycle of this established TDMA frame.

In addition, communication control units 305 and 407 between each base station and mobile station
monitors the FS included in the channel burst signal of the received control signal, and each base station monitors the time slot interval of the TDMA frame between each base station and mobile station within the wireless zone of its own base station. There is.

In this state, when the network control unit 301 of each base station receives an incoming signal from the network side, the communication control unit 301
5 outputs a frequency instruction signal of a random frequency to the synthesizer sections 313 and 323, and causes the reception frequency in the reception unit 320 to be randomly switched.

Then, the communication control unit 3 receives the electric field detection signal from the reception unit 321 in each time slot of the switched frequency.
05 monitors for more than an ITDMA frame (T seconds), and when an electric field is detected in any time slot, the same electric field detection signal as described above is monitored for other frequencies.

In this way, when the time slot in which no electric field is detected in both the up and down directions is detected by the communication control unit 305, it recognizes this time slot as an empty channel and generates an incoming call message containing information about the empty channel. TDM
It outputs to the A/TDD processing section 306 and also outputs a transmission/reception frequency instruction signal to the synthesizer sections 313 and 323 so as to return the oscillation frequency to the fixed carrier for control signal transmission.

TD that received the incoming call message from the communication control unit 305
MA/TDD processing unit 306 generates a channel burst signal as a control signal including this incoming call message.

Then, at the same time as outputting a transmission start signal to the transmitter 312 and the anti-nano inch 340, the communication controller 3
05 modulates the channel burst signal in the modulator 311 using a TDMA frame determined based on the timing of the timing pulse from the clock oscillation circuit 304.
, the transmitter 312, the antenna 340, and the antenna 330 to the destination mobile station.

The reception section 421 of the mobile station, which receives this channel burst signal using a fixed carrier for transmitting control signals, demodulates the received channel burst signal at the demodulation section 422 and converts it into TD.
Output to MA/TDD processing unit 408 and perform TDMA/TDD
Processing section 408 outputs the free channel information included in this channel burst signal to communication control section 407 .

The communication control unit 407 checks whether the channel indicated by the free channel information can be used or not using an operation similar to the search operation for a free channel by the communication control unit 305 of the base station, and confirms that the channel is free. If so, generate an incoming call acknowledgment message containing information on the vacant channel whose availability has been confirmed, and send it to T.
It is output to the DMA/TDD processing section 408.

On the other hand, if the channel indicated by the above-mentioned free channel information is not free, the communication control unit 407 searches for another free channel using the same operation as the search operation for a free channel by the communication control unit 305 of the base station. TDMA/
It is output to the TDD processing unit 408.

Further, the communication control unit 407 receives the incoming call confirmation message,
Alternatively, the incoming call denial message is sent to the TDMA/TDD processing unit 408.
At the same time as output to synthesizer section 413, 423
Then, it outputs a transmit/receive frequency instruction signal that instructs the oscillation frequency to return to the oscillation frequency used during standby.

Then, the TDMA/TDD processing unit 408 outputs a transmission activation signal to the transmitting unit 312 and the antenna switch 440 in response to the input of the incoming call confirmation message or the incoming call denial message, and further outputs a transmission activation signal to the transmitting unit 312 and the antenna switch 440. A channel burst signal as a control signal including a call denial message is transmitted to the modulator 4.
11, the standby signal is output to the nearest base station via the transmitter 412, antenna switch 440, and antenna 430 at the current transmission and reception frequency.

When the base station receives a channel burst signal as a control signal containing an incoming call acknowledgment message from the mobile station, it starts communication with the mobile station on the vacant channel indicated by this incoming call acknowledgment message, and thereafter , the communication control unit 305 synchronizes the synthesizer unit 313 with the timing of the vacant channel.
．． 323 and antenna switch 340 are appropriately switched and controlled.

On the other hand, when the base station receives a channel burst signal as a control signal containing an incoming call denial message from the mobile station, the channel indicated by another free channel information indicated in the incoming call denial message is The communication control unit 305 confirms whether or not it can be used by performing the same operation as described above.

If a free channel is confirmed, communication with the mobile station will be started on the free channel indicated in the 20 incoming call confirmation message, and if it is already used by another base station or mobile station, , and then searches for other free channels, and repeats this loop until the network side connects to the line, or for an appropriate period of time.

Note that when a call is made from the mobile station side, a search for an empty channel is performed under the control of the communication control unit 407 on the mobile station side, and a call request message containing information on the detected empty channel is sent as described above. It is generated by the communication control unit 407 in place of an incoming call confirmation message or incoming call denial message when a call is received from the network side.

Then, the channel burst signal including the 20 call request message is transmitted to the TDMA/TDD processing unit 408 and the transmission unit 41.
0, by being sent to the nearest base station via the antenna switch 440, antenna 430, and mobile radio line, and from then on, the base station side receives the incoming call confirmation message or the incoming call denial message in the same way. The following operations are performed, and communication between the base station and the mobile station is started.

3. Interference avoidance operation during communication When the negotiation regarding the connection between the base station and the mobile station as described above is completed, the wireless link between the base station and the mobile station is established, and the communication between the base station and the mobile station is established. is started.

However, as mentioned earlier, each base station generates timing pulses individually, so multiple base stations (mobile stations)
When base stations communicate using different time slots of the same carrier, channel collisions with other base stations (mobile stations) may occur over time.

Therefore, when communication between the base station and mobile station starts,
Thereafter, the channels used by other base stations (mobile stations) are monitored, collisions are predicted, and collision avoidance operations based on this are performed as described below.

3-1. First example of collision avoidance operation: Each base station and mobile station that have started communication are on a channel other than the channel (carrier and time slot pair) acquired by the own station, that is, on the same carrier as the channel acquired by the own station. In other time slots, it is in the receiving state.

In this reception state area, the base station detects electric fields in time slots surrounding the time slot acquired by the base station, that is, monitors the presence or absence of channel burst signals transmitted using the surrounding time slots. , and is performed under the control of the communication control units 305 and 407 of each mobile station.

Through this monitoring, the communication control units 305 and 407 of each station transmit and receive the rear R portion of the channel burst signal transmitted in each time slot and the transmitter/receiver for the time slot before the channel acquired by the station. The time interval with the front R portion of the channel burst signal is measured.

On the other hand, the communication control units 305 and 407 of each station control the R part of the front edge of the channel burst signal transmitted and received by the own station and the channel transmitted in each time slot with respect to the time slot after the channel acquired by the own station. The time interval with the front R portion of the burst signal is measured.

Then, when the above-mentioned measured time interval becomes gradually shorter and the time predetermined by the communication control unit 305, 407 is reduced to seconds (t<<1 time slot), it becomes the same as the channel acquired by the own station. Search for an empty time slot in the carrier using a time slot other than the time slot acquired by the local station, and use the information of the searched next candidate time slot to send a signal to the opposite station.
The opposite station is notified using the 5ACCH area of the channel burst signal.

The opposite station that has received the information about the next candidate time slot checks again whether the next candidate time slot is vacant, and if it is vacant, returns an acknowledgment to the opposite station via 5ACCH, and sends an acknowledgment to the base station and the mobile station. Both stations synchronize and transition to the next candidate time slot.

In this case, in order to prevent a shift in the transmission timing of communication signals such as voice signals due to the transition of the transmission/reception time slot, this timing shift is absorbed by the buffer memory of each station before transmitting the signal.

On the other hand, if there is no vacant time slot on the same carrier, the receiving sections 321 and 421 of each station
．． 407, the receiving frequency is changed, an empty time slot in another carrier is searched, and the detected empty time slot in the other carrier is designated as the next candidate channel, and the opposite station is notified by the same operation as described above.

In addition, if each station recognizes that the next candidate channel notified from the opposite station as described above is already being used by another base station or mobile station, each station on the side that recognized this Search the channel and send 5ACCH to the opposite station
The next candidate channel is specified in the negative response message sent back using the field.

3-2. Second Collision Avoidance Operation Side In the first collision avoidance operation example above, a method of predicting a collision by detecting the electric field of the channel burst signal between the own station and other stations was shown. There is a method that utilizes the FS included in the channel burst signal used.

A frame synchronization detection circuit (not shown) in the TDMA/TDD processing unit 306, 408 of each station performs FS detection in order to establish frame synchronization between the own station and its opposite station.

However, this detection is not performed after frame synchronization is established between the own station and its opposite station, and each station's TDMA/
The frame synchronization detection circuits in the TDD processing units 306 and 408 are not used after the frame synchronization is established.

Therefore, each station monitors the FS of channel burst signals sent by other stations in other time slots on the same carrier as the channel acquired by the station, and compares the FS sent by other stations and the FS sent by the own station. By measuring the time interval with the FS, the mobile station predicts a collision with another station's channel and changes the channel used by the local station, similarly to the first example of collision avoidance operation.

4. Countermeasures against frequent collision avoidance operations As mentioned in the section 4, in the receiving section 321 and 421 of each station,
It is possible to determine with a certain degree of accuracy the presence or absence of a received signal in each time slot of the same frequency as the channel used by the own station, as well as the reception level of the received signal.

Therefore, interference waves from other stations using a channel that is predicted to collide with the channel used by the own station, which is recognized by the operations shown in the first and second collision avoidance operation examples above. and the desired wave from the opposite station on the channel used by the local station, the receiving units 321.421 detect the respective reception levels, and transmit the electric field detection signals related to the detected reception levels to the communication control unit 305.421. 407.

Then, for example, 3 bits of information of the electric field detection signal (
However, if the received level of the desired wave is 5 levels or more higher than the received level of the interfering wave, the collision between the desired wave and the interfering wave is ignored.

This makes it possible to prevent unnecessary channel changes after communication has started, and to prevent interference avoidance operations from occurring frequently.

Effects of the Invention As described above, according to the present invention, a plurality of base stations that are connected to a network and generate synchronization independently of each other, and mobile stations that receive services from these base stations are connected by mobile radio links. Communication signal transmission consisting of a set of frequencies and time slots, which allows each base station to select the frequency and time slot to be used from among a plurality of frequencies and a plurality of time slots in each frequency. Multi-channel time-division multiplexing/hour-minute side duplex communication is performed using the same channel, and each base station and each mobile station uses it to receive communication signals directed to their own station. Using a different time slot with the same frequency as the channel, the own station receives the communication signal of another station that is communicating independently and in synchronization with the own station, and the time slot used by the other station and the above-mentioned own station Measure the interval between the time slots being used, and based on this measurement result, predict the collision between the time slots used by the local station and the time slots used by other stations, and calculate the prediction. Based on the results, before a collision occurs between the time slot used by the own station and the time slot used by the other station, all stations detect unused channels. The channel used by the own station and the opposing station with which the own station communicates is simultaneously changed to the detected empty channel.

Furthermore, the present invention provides independent synchronization for each base station and each mobile station by using different time slots with the same frequency as the channel used for receiving communication signals directed to the own station. The communication signals of other stations communicating with the station and the communication signals directed to the own station are received, the received signal level of each of these communication signals is detected, and the time slot used by the above station and the communication signal of the above station are detected. When a collision with a time slot used by another station is predicted, the reception level of the communication signal of the other station is compared with the reception level of the communication signal for the own station, and based on this comparison, the reception level of the communication signal of the other station is predicted. When the station recognizes that the receiving level of the communication signal is sufficient to interfere with the communication signal directed to the own station, the time slot used by the own station and the time slot used by the other station are determined. Before a collision occurs with the time slot that is currently being used, all stations detect an unused free channel, and use the detected free channel with the above-mentioned own station and the opposite station with which it is communicating. The channels used in the ``channels'' are now transitioned at the same time.

Therefore, the period of the carrier used by other base stations is detected and compared with the period of the carrier used by the own base station.
Based on this, each base station establishes frame synchronization by generating different transmission locks by detecting the proximity to carrier time slots used by other base stations. Before a collision occurs between the time slot currently being used and the time slot being used by another base station, the channel to be used can be changed by reselecting another free channel. You can avoid collisions with the timeslots used in
Therefore, multi-channel T
The DMA method can be easily introduced.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a TDMA frame, which is a transmission format of an 8-channel transition MA/TDD method on a mobile radio line, in a mobile cell phone system using a dynamic channel allocation method according to an embodiment of the present invention. , FIG. 2 is an explanatory diagram showing the structure of a channel burst signal transmitted in each time slot in the TDMA frame of FIG. 1, and FIG. 3 is an explanatory diagram showing a dynamic channel allocation method according to an embodiment of the present invention. FIG. 4 is a block diagram showing a schematic configuration of a base station in a mobile cell phone system used in the present invention. FIG. 4 shows a schematic structure of a mobile station in a mobile cell phone system using a dynamic channel allocation method according to an embodiment of the present invention. The explanatory diagram, Figure 5, shows the same carrier with two different
A timing chart showing the temporal relationship of mutual time slots at the time when two base stations use and start communication;
FIG. 6 is a timing chart showing a state in which a collision occurs over time between the time slots used by the two base stations in FIG. KSI, KS2...Base station, PSL, FS2...
...Mobile station, TS, TSl, TS2. ..., T
S8...Time slot, R...Ramp (reception rising point, reception falling point), FS...
...Frame synchronization signal. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 6 Figure 4 Figure 5 Figure 6

Claims (6)

[Claims] (1) Communication via mobile radio links between multiple base stations connected to a network that generate synchronization independently of each other and mobile stations receiving services from these base stations is carried out for each base station.
A multi-channel system using a communication signal transmission channel consisting of a frequency and time slot set that allows the user to select the frequency and time slot to be used from among multiple frequencies and multiple time slots for each frequency. The time division multiplexing/time division duplex communication method is used, and each base station and each mobile station uses a different time slot on the same frequency as the channel used to receive communication signals directed to the own station. , receives the communication signals of other stations that are communicating independently and synchronously with the local station, and calculates the interval between the time slots used by the other stations and the time slots used by the local station. Measure and based on this measurement result,
The collision between the time slot used by the own station and the time slot used by the other station is predicted, and based on the prediction result, the time slot used by the own station and the time slot used by the other station are predicted. Before a collision with the time slot being used occurs, all stations detect unused free channels, and the above-mentioned own station and the communication partner of the own station use the detected free channels. A dynamic channel allocation method that simultaneously transitions the channel used by the opposing station. (2) Each of the above base stations and mobile stations uses a different time slot with the same frequency as the channel used to receive communication signals directed to the own station, and communicates with independent synchronization to the own station. The communication signal of the other station is received and the received signal level is detected, and from the detected communication signal level, the reception rise and reception fall points of the communication signal of the other station are recognized, and based on this, Detects the leading edge and trailing edge of the time slot used by the other station, and uses the detected leading edge and trailing edge of the time slot used by the other station. , the above claim recognizes the position of the time slot used by the other station and recognizes the interval between the time slot used by the own station and the time slot used by the other station. Dynamic channel allocation method according to item (1). (3) Each of the base stations and mobile stations mentioned above uses a different time slot with the same frequency as the channel used to receive communication signals directed to the own station, and communicates with independent synchronization to the own station. A frame synchronization signal included in the communication signal of the other station is detected based on the detected frame synchronization signal included in the communication signal of the other station. , the above claim recognizes the position of the time slot used by the other station and recognizes the interval between the time slot used by the own station and the time slot used by the other station. Dynamic channel allocation method according to item (1). (4) Each of the above base stations and mobile stations uses a different time slot with the same frequency as the channel used to receive communication signals directed to the own station, and communicates with independent synchronization to the own station. It receives the communication signals of other stations that are currently operating and the communication signals directed toward the own station, detects the received signal level of each of these communication signals, and determines the time slot that the own station is using and the time slot that the other station is using. When a collision with the time slot being used is predicted, the reception level of the communication signal of the other station is compared with the reception level of the communication signal for the own station, and based on this comparison, the communication signal of the other station is When the reception level of the signal is recognized to be sufficient to interfere with the communication signal directed to the above-mentioned own station, the time slot used by the above-mentioned own station and the time slot used by the above-mentioned other station Before a collision occurs, all stations detect an unused free channel, and use the detected free channel between the above station and the opposite station with which the station communicates. Claim (1) wherein the channels are caused to transition simultaneously.
The dynamic channel allocation method described in (3) to (3) above. (5) At a certain point in time before the leading edge of the time slot used for receiving communication signals directed to the base station and each mobile station, and at a certain point in time from the trailing edge of the time slot Set a certain point in the rear as the identification point, and use a different time slot with the same frequency as the channel used to receive the communication signal directed to the own station, and communicate with the own station with independent synchronization. When it is detected that the leading edge, trailing edge, or frame synchronization signal area of the time slot of another station is located on the side of the time slot used by the own station from the above identification point. , the dynamic channel allocation according to claims (1) to (4), wherein a prediction is made that a collision will occur between a time slot used by the own station and a time slot used by the other station. Method. (6) The leading edge of the time slot used by each base station and each mobile station to receive communication signals directed to its own station;
It uses the trailing edge or frame synchronization signal area and a different time slot with the same frequency as the channel used to receive communication signals directed to its own station, and communicates with independent synchronization to its own station. The position of the time slot used by the own station and the time slot used by the other station are determined by recognizing the leading edge, trailing edge, or frame synchronization signal area of the time slot of the other station. The position is recognized, and the leading edge, trailing edge, or frame synchronization signal area of the time slot used by the own station, and the leading edge, trailing edge of the time slot used by the other station. Department,
Alternatively, by detecting the relative phase change over time with the frame synchronization signal area, calculate the relative moving speed of the time slot used by the other station as seen from the time slot side used by the own station. Then, the calculated relative moving speed of the time slot used by the other station as seen from the time slot side used by the own station, and the recognized above time slot of the time slot used by the own station. Based on the position and the position of the time slot used by the other station, the time slot used for receiving the communication signal for the own station collides with the time slot used by the other station. 6. The dynamic channel allocation method according to claim 1, wherein the time point is predicted and calculated.